Study Designs

Question 1

Describe the difference bteween causality and association

Answer 1

Causality: The understanding that an exposure leads to an outcome

Association: The understanding that there is a relationship between two or more variables without affecting the others value

Question 2

In general, studies can be analysed by the reader using a pneumonic. Explain this pneumonic

Answer 2

Population

Intervention/indicator

Control/comparator

Outcome

Question 3

Name two types of intervention studies

Answer 3

Randomised trials

Non-randomised trials

Question 4

Name 4 observational studies and identify which are analytical and which are descriptive

Answer 4

Anatlytical

• Ecological
• Case control
• Cohort
• Cross-sectional

Descriptive

• Cohort
• Cross-sectional

Question 5

Describe 3 advantages of randomised clinical trials

Answer 5

1. Can make causality observations
2. ↓Allocation bias
3. ↓confounding

Question 6

Describe 5 disadvantages of randomised clinical trials

Answer 6

1. ↑dropout rates
2. needs ethical review
   
   1. link between smoking and lung cancer
3. ↓compliance to intervention
4. Costly and time-consuming
5. Difficult to get representative or equal sample sizes
   
   1. e.g. only difference between groups should be intervention (same ratio of female to male or ethnicity etc)

Question 7

Describe the advantages of using a cross-sectional study

Answer 7

1. Hypothesis generating
2. Can examine multiple outcomes
3. Study multiple exposures
4. Quick

Question 8

Describe the disadvantages of using a cross-sectional study

Answer 8

1. Unsuitable for rare disease
2. Reverse Causality
3. Bias:
   
   1. Selection
   2. Sampling
   3. Response

Question 9

Describe the advantages of case-control studies

Answer 9

Observational studies

1. Good with rare disease
2. Quick and cheap

Question 10

Describe the disadvantages of using case control studies

Answer 10

1. Difficult to find the correct controls
2. Exposure assessment errors (bias)
   
   1. recall
   2. recording
   3. social desirability bias (response bias - over reporting good and under reporting bad)

Question 11

Describe the advantages of using cohort studies

Answer 11

1. Know exposure precedes disease
2. Can studty many outcomes from single exposure
3. Good with rare exposures
4. Direct measure of incidence
5. Measures time relationship with exposure and outcome

Question 12

Describe the disadvantages of using cohort studies

Answer 12

1. Time consuming
2. Loss to follow up
3. Expensive

Question 13

Describe the advantages of using ecological studies

Answer 13

1. Good with rare disease investigation
2. Quick and cheap

Question 14

Describe an advantage and disadvantage of systematic reviews and metanalysis

Answer 14

Advantage: cheap

Disdadvantager: Publication bias

Question 15

Describe the disadvantages of using ecological studies

Answer 15

1. Ecological fallacy
   
   1. Not useful for attributing casual relationship at individual level

Question 16

Draw a diagram to represent a randomised controll trial study

Answer 16

Question 17

Draw a diagram to represent a cross-sectional study

Answer 17

Question 18

Draw a diagram to represent a cohrt study

Answer 18

Question 19

Draw a diagram to represent a case-control study

Answer 19